You can try to put some one unit player clips in front of every face of the curve, for some reason those have always seemed a bit smoother to me. Otherwise you can try to make the brushes into a prop with propper, might also help making it a bit smoother. If worst comes to worst look up a surf map tutorial, make a ramp that isn't sticky, and stretch it WAY up so that it is almost vertical (or just leave it kind of rampy could be cool, idk how you're using it in the map tho).